diff --git a/core/modules/system/js/system.date.js b/core/modules/system/js/system.date.js
index 678614d..17db66c 100644
--- a/core/modules/system/js/system.date.js
+++ b/core/modules/system/js/system.date.js
@@ -41,7 +41,7 @@
           return dateFormats[key] ? dateFormats[key] : value;
         });
 
-        $preview.html(dateString);
+        $preview.html(Drupal.checkPlain(dateString));
         $target.toggleClass('js-hide', !dateString.length);
       }